raid 0 and 1 on same disks

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pitch4pd

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Jul 22, 2007
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Hello everyone,

I have an odd question that I dont think is possible but thought it wouldnt hurt to ask. I just picked up 2 Hitachi Deskstar e7k500 500gb hard drives to use on my Abit IP35 Pro m/b. I would like to setup 3 partitions on the drive, the first 2 partitions would be raid 0's each 250gb each. First partition for games and OS, the second partition for fast file storage(rar files from newgroups etc). Then I would like the third partition of 250gb be in Raid 1 for backup purposes(files I don't want to lose).

This sounds impossible in my head but I just want to check to see if it is as tonight I am going to install the hard drives. Either in 3 Raid 0's or the aforementioned way above.

Thanks,
Charles
 
It's possible but there is a catch, you can't do it using intel raid matrix (the mobos built in raid) you would need a dedicated raid controller, another solution would be to use any *nix os, all of them are capable of setting up raid on pieces of a hard drive.
 
Yep - possible depending on the controller but generally a bad idea.
 
Intel had an option to run RAID-0 on one set of partitions and RAID-1 on the other, called `matrix raid' or something.
 
So my MB doesnt support it I see. Well as usual another great idea gone to waste! As for performance it would work out just the same, I would be only using one partition at a time for the most parts. While playing a game I would be on the faster first partition of Raid 0, when unraring files I would be using just the second partition of Raid 0. Then when moving file to the Raid 1 portion it would suffer dearly in performance, but who need fast backups? I usualy set those task's to take place as I am sleeping!

Well thanks guys, gonna get tearing things apart and hopefully Vista Business 64 works smooth (doubt it) will post back once I get things running again.
 
pitch4pd said:
Then when moving file to the Raid 1 portion it would suffer dearly in performance...
Click to expand...
True, but it wouldn't be that awful. The system would have to:
1. read from source array into a buffer
2. write from buffer into destination array
3. goto 1 until finished

That's no different from:
- copying data between partitions on a non-RAID disk
- copying data on the same filesystem

As long as the OS uses a decently-sized buffer, seeks between partitions should be relatively infrequent, so seek time is almost negligible. Thus, the average I/O speed should be very close to the harmonic mean of the speeds of the two participating arrays:
avg = 2 * speed1 * speed2 / (speed1 + speed2)
...and the total overall speed should be half that (since the data has to be read and then written):
total = avg / 2
...thus:
total = speed1 * speed2 / (speed1 + speed2)

For example, say the RAID0 can read at 150 MB/s and the RAID1 can write at 70MB/s. The overall speed would be
total = 150 * 70 / (150 + 70)
total = 47.72 MB/s

I wouldn't consider that to be terrible for infrequent usage. :)
...unless I'm missing something...

-Corey
 
Sounds good to me for performance. But oh well I tried and the raid controller wouldnt even give me an option of anything else than Raid 0 after I created the first Raid 0 partition. Looks like I am out of luck, oh well I will just have to make DVD's of stuff I never want to lose.

As for performance , HDTach read 215 mb/s burst and 150 average. With 9.2 m/s seek time, awesome stuff I think. That was until I loaded vista 64 and ran hd tach again (under compatibilty mode) the graph was all messed up so I just assume it was compatibilty modes fault. All I know is Vista 64 is running fast and I just wish more programs were 64 bit.

Charles
 
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